On Friday, Republican presidential frontrunner and real estate billionaire Donald Trump postponed a planned rally at the University of Illinois at Chicago after thousands of protesters gathered outside the venue.

According to the Chicago Tribune, Trump said security concerns drove his decision after fights broke out between attendees and protesters. He told MSNBC he "felt that it was just safer ... Rather than having everybody get in and mix it up, I thought it would be a wise thing, after speaking with law enforcement, a wise thing to postpone the rally."

But according to Time, Chicago police denied they had advised Trump to cancel the rally, or even that they were involved in the decision at all.

Tribune photographer E. Jason Wambsgans caught what might be the iconic photo of the night — a Trump supporter raising her right hand in salute in an image that carries unmistakable overtones of Nazi-era Germany.

The woman in the photo, German-born 69-year-old Birgitt Peterson, told the New York Times the gesture was intentional, she is not a Nazi and supports Trump's efforts to "break up the Republican Party." Peterson says the salute was a counter-protest against individuals at the rally with signs comparing Trump to German dictator Adolf Hitler.

"They said Trump is a second Hitler," she told the Times. "I said do you know what that sign stands for? Do you know who Hitler really was? ... I make the point that they are demonstrating something they had no knowledge about. If you want to do it right, you do it right."

Trump-Nazi comparisons recently made the news after the candidate asked Florida voters to raise their right hands and pledge loyalty to his campaign.

Trump's son, Donald Trump Jr., took to Twitter to mock the protesters as the "participation medal/micro-aggression generation" before being quickly shut down by singer-songwriter John Legend.

@DonaldJTrumpJr I think they were protesting your racist father. This isn't complicated.

Trump himself suggested the cancelled rally would only energize his supporters, calling the protesters "thugs."

The organized group of people, many of them thugs, who shut down our First Amendment rights in Chicago, have totally energized America!

At a recent debate in Miami, the candidate responded to a question about widespread violence reported at his rallies by praising the "tremendous love and passion for the country" of his supporters and adding, "When they see what's going on in this country, they have anger that's unbelievable."

Update: March 12, 2015 at 5:35 p.m.

This article has been updated to include a statement from Birgitt Peterson, the woman in the photo, explaining why she chose to re-enact the Nazi salute.